Results: Sleep Less, Eat More
While the sleep-deprived group ate the extra 549 calories daily, the comparison group actually ate about 143 fewer calories daily than usual.
The researchers tracked how active each group was. "A lot of people assume if they are awake longer, they will move more and burn more calories," Calvin tells WebMD.
Not so, he found. He didn't find much difference in activity expenditure between the sleep-deprived group and the group that slept as much as they wanted.
Sleep deprivation was linked with somewhat higher levels of leptin, the hormone that tells your brain you are full. It was linked to somewhat lower levels of ghrelin, the hormone that tells your brain you are hungry.
Calvin expected the opposite. "We thought sleep deprivation would reduce leptin and increase ghrelin," he says. That would make people feel hungrier and less full. However, the increase and decrease were slight, he says.
It appears the hormone changes may be a consequence, rather than a cause, of eating extra calories, he says.
The link between sleep deprivation and extra calories may be more complicated than scientists thought, he says.
Until more research is in, Calvin says, "If you are looking to maintain a healthy weight or lose weight, I think getting adequate sleep may be very important."
Sleep Deprivation And Eating: Perspective
The study is ''consistent with previous findings," says Eve Van Cauter, PhD, a professor of medicine at the University of Chicago. She has also researched the topic.
"The size of the increase in calorie intake is enormous," she says, referring to the 549 additional calories.
She is not surprised that the leptin levels went up and the ghrelin went down in the sleep-deprived group.
"The increase in leptin is due to the weight they gained during the week," she says. "When you eat 549 extra calories a day for eight days, there is no way their weight would have been stable."
"When you put on more weight, that additional weight comes in the form of fat," she says. "Leptin levels are proportionate to fat."